Amazon.com: Fanbiya Armor Case for ASUS ROG Phone 3 - TPU Frame Clear A-Grade Acrylic Back Compatibl...This is the case that I currently use. The padding on the sides seem to be decent, and it extends up a bit so you don't have to worry about the phone falling on the screen if you drop it. Back is clear so Aura RGB shows. There's space cut out for the Air Triggers, side port, air vent, and mics. Bottom USB-C port has a flap to cover it.
Pretty nice, overall. It can be used with the AeroActive cooler, though it cannot close completely due to the padding.
My only complaint is that it cannot be used with the TwinView Dock.